Process of burning out invested models.



T. W. MAVES.

PROCESS 0F BURNING OU INVESTED MODELS APPLLCATION FILED SEP? 23. 1918.

Patented J 2,111. 14, l1919.

' ernten.

THEODORE WILLIM MAVES, 0F MINNEAPOLIS, MINNESOTA.

PROCESS OFBURNING OUT INVESTED MODELS.

Application led September 23. 1918.

fo all whom t may concern:

Be it known that I, THEoDoRE IV. Mavns, a citizen of the United States,resident of Minneapolis, county of Hennepin, State of Minnesota, haveinvented certain new' and useful Improvements in Processes of BuruingOut Invested Models, of which the fol lowingis a specification.. y

In making dental castings, it has beencustomary to provide a flask inwhich a wax model or pattern of the shape of the cavity to be filled orof the form of the desired casting is placed and surrounded by what isknown as investment material, with a sprue rod mounted in the wax modeland eX- lending outwardly through the investment material. The Wax modelis then melted to be absorbed by the surrounding material, and the screwrod having been previously removed, a matrix will be formed into whichthe molten metal is poured to form the desired casting or inlay.

The object of my present invention is to provide a process of meltingthe wax model lo the end that the matrix can be neatly and expeditiouslyformed within the investment material and a perfectly formed casting be.subsequently obtained.

The invention consists generally in the process set forth in theclaims.'

In the accompanying drawings forming part of this specification,

Figure l is a vertical sectional view through an apparatus which Iprefer to employ in carrying out my process.

Fig. 2 is a plan view. with the cover removed, showing the support forthe flasks above the heater,

Fig. 3 is a plan view of the heater,

Figs. 4 and 5 are detail views of the flask hole cover.

.In carryin, ,r out my process, I prefer to employ the apparatussubstantially as shown herein and which I 'will now describe in dc-`tail. In such an apparatus the tlask supporting plate or carrier must bea certain predetermined distance from the heater to obtain the bestresults-not too near or the wax will be burned ou( or melted tooquickly, and not too far away or the wax will be melted, too slowly andtoo unevenly to obtain a finely finished casting. A degree of heat thatis too low to uniformly melt the wax will be fatal to the successfuloperation" of the device, for if the melting is vnot uniformly obtained,the casting will Specication of Letters Patent.,

Patented Jan. 14n, 1919.

serial No. 255,310.

the wax pattern and hence will not lit the tooth. Overheating will causethe investment to crack and produce a defective casting. The bestresults are obtained by subjecting the walls of the flask to a slow,gradual heat which will melt the wax uniformly and evenly and by sodoing I am able to produce a smooth, accurately formed casting whichwill be an exact duplicate of the wax and a perfect fit for the tooth.

Referring now to the accompanying drawing for the detailed description,2 represents the base of the heater, which I employ in carrying out myprocess, having suitable supporting legs and provided in its'uppersurface with a series of transverse grooves" or recesses a in which aresistance coll 5 is placed and embedded in 'a suitable plastic material(l. The ends of the coil are in circuit with an electric conductor 7through which a current is passed to heat the resistance wire 5 and thespace above the heater forming the oven. The resistance coil is so madeor formed that when the current is turned on the oven will be heated toa certain telnperature. which I have found best suited fory uniformlymelting the waX.

By equipping the heater with a coil for producing a certain degree oftemperature, I am able to determine how long the flask should bein theoven to melt the model. The base or bed of the heater has preferably arecess or shoulder therein at 8 whercon an inclosing easing t) isseated. This casing is preferably made of metal, rectangular i1: form,to lit snugly down over the top of the base and form a-heating chamberor oven 10 above the base. Ledges 11, preferably of angle bar, aresecured to the casing 9, prcferably at a point midway between the topand bottom of the casing and form supports 'for a floor plate 12 that isloosely seated on the ledges l1 and forms the top or roof of the ovenchamber 10. This plate 12 is provided with a comparativel)l largecentral opening 13 and a series of smaller openings 14 arranged aroundit, and I preferably provide flanges 15 and 16 encircling these openingsand spaced from the edges thereof to form ribs or ledges 17. The flanges15 and 1G have openings 18 therein and'cover plates 1f) fit within theflanges and close the 'openings in the plate l2 and have linger grips 2Owhich project through the openings 18. These cover plates close theopenings until such time as the operator desires to insert a flasktherein, when the plate vvill be removed and theask with the Wax modeltherein placed ,in the opening with its lower portion depending into theoven 10. The lower portion'of the flask Will be suiiioiently near thetop of the heater so that the Wax Will be melted and absorbed by theinvestment material. By providing openings of di'erent sizes in theplate 12, I adapt the apparatus for flasks of' different diameter. Thetop of the casing is preferablyv closed by a cover plate 21 having aseries of ventholes 22 therein, one above each opening, and a hand grip24 Which' has a central vent opening 25. When this cover is removed,access may be had to the plate'12 and the ask therein.

` This plate, as shown, is preferably supported about midway between thetop and bottom of the casing so there will be ample room above thesupporting plate for the top of the flasks and for the sprue rods.

By means of this process I am able to expose the Walls of the flask orflasks to a uniform gradual heat, the duration of which may be regulatedaccording to the character of the Work and the size of the model to be@opten of this notent may be obtained for momes melted. The Wax absorbedby the investment material through this process Will leave a smoothmatrix from which an accurate, perfectly formed casting can be made.

l claim as my invention:

1. A process of burning out or melting y invested models `which consistsin placlng a taining the invested model Within a closed oven andsubjecting the Walls of the flask to a dry heat. n

1n Witness Whereoff have hereunto set my handthis 20th day of September,1918.

THEODORE WILLIAM MAVES. V

rive cents enea, by addressing the 6"G@misuranoner or Patente,

Warrington, E). @it

flask .containing the invested model Within f

